The Jump Stop should be whatever size your front derailleur clamp was, but since that bike didn't use a clamp-on front derailleur you'll have to measure the seat tube yourself. Is the seat tube round in the area across from the top of your middle ring?

love the simple sets for 1x9- I have set these up on a Nomad and an Intense 6.6 and had pretty good results- not great. These types of set ups work best on hard tails or cross bikes- just too many moving parts.